Science Inventory

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We assessed the extent and characteristics of geographically isolated wetlands (i.e., wetlands completely surrounded by upland) in a series of drainage basins in the urban northeast U.S. We employed a random sampling design that stratifies study sites according to their degree of urbanization and allows the extrapolation of results to other watersheds of known urbanization in regions of similar topography, surficial geology, and glacial history. The density of isolated wetlands in our sample of southern New England watersheds averaged between 1.29 ± 0.54 and 1.63 ± 0.70 wetlands km-2 and comprised 19.6 – 24.2 % of all wetlands and wetland complexes. Isolated wetlands were smaller than those connected to other waters (non-isolated), and accounted for 5.2 – 6.9 % of the total wetland area in the watersheds. The area of isolated wetlands as a percent of all wetland area significantly increased with increasing watershed urbanization (r2 = 0.58, p = 0.01). Isolated wetlands were predominantly deciduous forested wetlands, and urban land cover in the 50 m buffer surrounding isolated wetlands was significantly higher than in the 50 m surrounding non-isolated wetlands. As distance from an isolated wetland increases, land cover becomes increasingly more urbanized with an accompanying loss in the extent of surrounding wetlands. These findings indicate that the process of urbanization, along with accompanying habitat fragmentation, may result in an increase in the vulnerability of wetlands to loss and degradation and therefore has implications for the management and conservation of geographically isolated wetlands.

Purpose/Objective:

This study assesses the extent and characteristics of geographically isolated wetlands in a series of drainage basins in the urban northeast U.S.. These wetlands exist more or less in isolation from other aqautic systems and have garnered recent attention as the focus of several U.S. Supreme Court opinions questioning their jurisdiction under the Clean Water Act (CWA). The vast majority of geographically isoloated wetlands have yet to be identified and mapped, and there is a need to assess their presence, extent, and properties. This is particularly true in urban watersheds, where wetlands may be at greater risk of becomning isolated as a result of habitat fragmentation through urbanization. We examined the density, area, wetland type and landscape setting of isolated wetlands in southern New England watersheds and report trends in these characteristics along a gradient of urbanization. Our Findings idicate that the process of urbanization, along with accompanying habitat fragmentation, may result in an increase in the vulnerability of geographically isoloated wetlands to loss and degradation and therefore has implications for their management and conservation.

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